The present invention involves microwave cooking. More particularly, the present invention is an apparatus for the electrical tuning of a cooking stack in a microwave oven.
The term cooking stack generally refers to a number of generally planar layers in a microwave oven during operation of the oven. A cooking stack can include a food product to be cooked, which may have several layers, along with any device for holding the food product (such as a support member and a lid), as well as an oven shelf and any air layers in the microwave oven between the oven floor and the lid or the top of the food product. For example, a typical cooking stack for cooking a frozen pizza may have several layers including the pizza sauce, the crust, a platform for holding the frozen pizza in the microwave oven, the oven shelf, and any air layer between the oven shelf and the oven floor. The platform for holding the pizza may typically include a pizza box in which the frozen pizza was purchased.
Heating of such food products in a microwave oven differs from heating foods in a conventional oven, and several problems can arise in achieving desired cooking performance. In a conventional oven, heat energy is applied to the exterior surface of the food and moves inward until the food is cooked. Thus, food cooked conventionally is typically hot on the outer surfaces and warm in the center.
Microwave cooking, on the other hand, involves absorption, by the food, of microwaves which characteristically penetrate the food much more deeply than does infrared radiation (heat). Also, in microwave cooking, the air temperature in the microwave oven may be relatively low. Therefore, it is not uncommon for food cooked in a microwave oven to be cool on the surfaces and much hotter in the center. This makes it difficult to brown food and make it crisp.
In order to facilitate browning and crisping of food in a microwave oven, devices known as susceptors have been developed. Susceptors are devices which, when exposed to microwave energy, become very hot. By placing a susceptor next to a food product in a microwave oven, the surface of the food product exposed to the susceptor is heated by the susceptor and thereby becomes crisp and brown.
However, susceptors do not solve all cooking problems associated with microwave ovens. There are also problems which arise from the location of standing waves in the microwave oven that affect cooking performance. The solution to these problems requires positioning certain layers of the cooking stack in the microwave oven so that the food product is located relative to the electric field in the microwave oven to achieve desired cooking performance.